Life Science and Chemical Analysis Solutions€¦ · 105.09 Peak True - sample "Cal 1 ASTM D5769",...
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Satisfying ASTM Method D5769: A Solution for Determination of High-Concentration Aromatic Compounds in Finished Gasolines LECO USA Corporation; Saint Joseph, Michigan Key Words: ASTM, Petroleum, Gasoline, Aromatics, Benchtop 1. Introduction ASTM D5769 is a widely accepted standard method used in the petroleum industry for the determination of benzene, toluene, and total aromatics in finished gasolines by GC-MS. A common difficulty encountered with this method is the concern with saturation of the ion source, which leads to non-linearity in calibration curves, especially for the quantification of high-concentration aromatics, such as toluene. LECO's Pegasus BT GC-TOFMS easily satisfies the ® method requirements for sensitivity, ion ratios, and calibration linearity, providing a solution for analysis of the aromatic compounds listed in ASTM D5769, without saturation of the ion source. Calibration curves were built for the standard method analytes, and then applied to samples with the addition of semi-quantification for similar analytes on a sample of 93-octane gasoline, as stipulated in the method. Life Science and Chemical Analysis Solutions Figure 1. Total aromatics were determined for a commercially available sample of 93-octane gasoline. The chromatogram with peak markers automatically placed for calibrated analytes and deuterated internal standards is shown, along with the required method checks exceeded by the Pegasus BT. 597.5 598 598.5 599 599.5 600 600.5 0 0.1e4 0.2e4 0.3e4 0.4e4 0.5e4 0.6e4 0.7e4 0.8e4 0.9e4 Time (s) Benzene, 1,4-diethyl- XIC(134.11±500ppm) Sensitivity Check XIC(134.11±500ppm) Sensitivity Check_2 XIC(134.11±500ppm) Sensitivity Check_3 100 200 300 400 500 600 700 0 1e8 2e8 Time (s) Benzene Toluene Ethylbenzene 1,2-Dimethylbenzene Benzene, (1-methylethyl)- Benzene, propyl- Benzene, 1-ethyl-2-methyl- Benzene, 1,2,3-trimethyl- Benzene, 1,4-diethyl- + butylbenzene Benzene, 1,2,4,5-tetramethyl- Naphthalene Naphthalene, 2-methyl- TIC S/N>5 Sensitivity Check 40 60 80 100 120 0 100 200 300 400 500 600 700 800 900 1000 M/Z 105.09 Peak True - sample "Cal 1 ASTM D5769", Benzene, 1,2,3-trimethyl-, at 584.071 s, Area (Abu ndance) Ion Abundance Check Ion (m/z) Required Intensity (%) Observed Intensity (%) 120 30-60 42 105 100 100 91 7-15 11 5 10 15 20 25 2.00 4.00 6.00 8.00 10.0 12.0 14.0 16.0 18.0 Concentration Ratio Cal 3 ASTM D5769 Cal 1 ASTM D5769 Cal 2 ASTM D5769 Cal 4 ASTM D5769 Cal 5 ASTM D5769 Calibration Check R > 0.99 2 Finished Gasoline Sample Total Aromatics: 10.75%
Transcript of Life Science and Chemical Analysis Solutions€¦ · 105.09 Peak True - sample "Cal 1 ASTM D5769",...
Satisfying ASTM Method D5769: A Solution for Determination ofHigh-Concentration Aromatic Compounds in Finished Gasolines
LECO USACorporation; Saint Joseph, Michigan
Key Words: ASTM, Petroleum, Gasoline, Aromatics, Benchtop
1. Introduction
ASTM D5769 is a widely accepted standard method used in the petroleum industry for the determination of benzene,toluene, and total aromatics in finished gasolines by GC-MS. A common difficulty encountered with this method is theconcern with saturation of the ion source, which leads to non-linearity in calibration curves, especially for thequantification of high-concentration aromatics, such as toluene. LECO's Pegasus BT GC-TOFMS easily satisfies the®
method requirements for sensitivity, ion ratios, and calibration linearity, providing a solution for analysis of the aromaticcompounds listed in ASTM D5769, without saturation of the ion source. Calibration curves were built for the standardmethod analytes, and then applied to samples with the addition of semi-quantification for similar analytes on a sample of93-octane gasoline, as stipulated in the method.
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Figure 1. Total aromatics were determined for a commercially available sample of 93-octane gasoline. The chromatogram with peakmarkers automatically placed for calibrated analytes and deuterated internal standards is shown, along with the required method checksexceeded by the Pegasus BT.
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Ion Abundance Check
Ion (m/z) RequiredIntensity (%)
ObservedIntensity (%)
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Cal 3 ASTM D5769
Cal 1 ASTM D5769
Cal 2 ASTM D5769
Cal 4 ASTM D5769
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Calibration Check
R > 0.992
Finished Gasoline Sample
Total Aromatics: 10.75%
2. Experimental
High-split, low-volume injections into the GC were utilized combined with full mass range acquisition with LECO'sPegasus BT GC-TOFMS, a benchtop time-of-flight mass spectrometer. ChromaTOF 's Target Analyte Find feature®
was used to automatically identify analytes of interest and quantify both calibrated and uncalibrated analytes usingQuantitation and Semi-Quantitation data processing tools.
Table 1. GC-TOFMS BT) Conditions(Pegasus
3. Results and Discussion
In order to meet the requirements for using ASTM D5769 to characterize a sample, three fundamental massspectrometer criteria must be met: sensitivity of 0.01 mass % for 1,4-diethylbenzene, achieving specified ionabundance ratios for key masses of 1,2,3-trimethylbenzene, and calibration linearity for all analytes.
The first requirement is stated in Section 6.2.3 of the method and stipulates that the signal-to-noise (S/N) ratio of0.01 mass % 1,4-diethylbenzene at mass 134 must be consistently greater than 5. As can be seen in Figure 2 andTable 2, repeat analysis shows that the instrument easily surpasses the required S/N of 5, with an average Peak S/Nof over 100.
Table 2. S/N Results for Replicates of 0.01 mass % 1,4-Diethylbenzene
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Gas Chromatograph Agilent 7890 with Agilent 7693 Liquid Autosampler
Injection 0.1 µl injection, split 1200:1 @ 260°C
Carrier Gas He @ 1.0 mL/min, Constant Flow
Column Rxi-1ms, 30 m x 0.25 mm i.d. x 1.00 µm coating (Restek, Bellefonte, PA, USA)
Oven Program 55°C (1 min), to 70°C @ 20°C/min (4 min), to 220°C @ 30°C/min (5 min)
Transfer Line 280 °C
Mass Spectrometer LECO Pegasus BT
Ion Source Temperature 250°C
Mass Range 35-550 m/z
Acquisition Rate 10 spectra/s
Figure 2. This chromatogram shows replicates of 0.01 mass %1,4-Diethylbenzene acquired for the sensitivity check.
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Name Quant Masses Quant S/N
1,4-Diethylbenzene XIC (134.11 ±500 ppm) 141
1,4-Diethylbenzene XIC (134.11 ±500 ppm) 151
1,4-Diethylbenzene XIC (134.11±500 ppm) 132
The second requirement stated in Section 9.2.5 of the method specifies expected ion ratios for 3 mass %1,2,3-Trimethylbenzene. This criterion is satisfied with values shown in Figure 3 and Table 3.
Table 3. Ion Ratio Results for 3 mass % 1,2,3-Trimethylbenzene
Linear calibration curves for all analytes are also required, with linear least-squares R values greater than 0.992
according to Section 9.3.3. Table 4 shows that the linear least-squares R values of each analyte exceed the criteria,2
with the average value at 0.99987. Figure 4 illustrates the excellent linearity achieved for a known problemcompound, toluene, with concentrations ranging from less than 2 mass % to over 20 mass %. The open-style source ofthe LECO BT avoids rollover due to saturation from these high-concentration aromatics, easily yielding linearPegasuscalibration curves for a wide dynamic range.
Table 4: R Values for Calibrated Analytes2
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Figure 3. Deconvoluted mass spectrum for the peak 1,2,3-Trimethylbenzene at 3 mass % level.
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Ion (m/z)Required
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Analyte R2
Benzene 0.99994
Toluene 0.99980
Ethylbenzene 0.99998
Benzene, 1,3-dimethyl- + 1,4-dimethyl 0.99998
1,2-Dimethylbenzene 0.99998
Benzene, (1-methylethyl)- 1.00000
Benzene, propyl- 1.00000
Benzene, 1-ethyl-3-methyl- 0.99950
Benzene, 1-ethyl-4-methyl- 0.99980
1,3,5-Trimethylbenzene 0.99996
Benzene, 1-ethyl-2-methyl- 0.99998
Benzene, 1,2,4-trimethyl- 1.00000
Benzene, 1,2,3-trimethyl- 0.99996
Indane 0.99988
Benzene, 1,4-diethyl- + butylbenzene 0.99994
Benzene, 1,2-diethyl- 0.99992
Benzene, 1,2,4,5-tetramethyl- 0.99992
Benzene, 1,2,3,5-tetramethyl- 0.99986
Naphthalene 0.99992
Naphthalene, 2-methyl- 0.99950
Naphthalene, 1-methyl- 0.99954
Average Value 0.99987
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The BT GC-TOFMS easily met all requirements necessary to properly analyze a finished gasoline sample forPegasustotal aromatics. All 23 calibrated analytes are labeled in the chromatogram below.
Figure 5. A chromatogram of 93-octane commercial gasoline is shown with peak markers automatically placed for the 23 calibratedanalytes.
Figure 4. Linear calibration curve generated for toluene, with R value of 0.9998.2
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Cal 3 ASTM D5769
Cal 1 ASTM D5769
Cal 2 ASTM D5769
Cal 4 ASTM D5769
Cal 5 ASTM D5769
LECO Corporation | 3000 Lakeview Avenue | St. Joseph, 49085 | Phone: 800-292-6141 | [email protected] • www.leco.com | -9001:2008 | -Q-994 |ISO HQ LECO LECOis a registered trademark of Corporation.
LECO LECO, Pegasus, and ChromaTOF are trademarks of Corporation.
Form No. 203-821-518 8/16- 0 © 2016 CorporationREV LECO
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Results for the commercial 93 octane gasoline fell within the expected ranges of 0.09 to 4% for benzene at 0.2%,1.0 to 13% for toluene, at 1.44%, and 9 to 42% for total aromatics determined at 10.75%, as can be seen in Table 5.
Table 5: Results for Aromatic Determination of 93 Octane Gasoline
Analyte Volume %
Benzene 0.20
Toluene 1.44
Ethylbenzene 0.20
Benzene, 1,3-dimethyl- + 1,4-dimethyl 0.64
1,2-Dimethylbenzene 0.31
Benzene, (1-methylethyl)- 0.09
Benzene, propyl- 0.09
Benzene, 1-ethyl-3-methyl- 0.11
Benzene, 1-ethyl-4-methyl- 0.22
1,3,5-Trimethylbenzene 0.11
Benzene, 1-ethyl-2-methyl- 0.16
Benzene, 1,2,4-trimethyl- 0.11
Benzene, 1,2,3-trimethyl- 0.25
Indane 0.13
Benzene, 1,4-diethyl- + butylbenzene 0.31
Benzene, 1,2-diethyl- 0.16
Benzene, 1,2,4,5-tetramethyl- 0.08
Benzene, 1,2,3,5-tetramethyl- 0.11
Naphthalene 1.98
Naphthalene, 2-methyl- 0.36
Naphthalene, 1-methyl- 0.18
Uncalibrated Indans 2.82
Uncalibrated C10-Benzenes 0.51
Uncalibrated C11-Benzenes 0.19
Uncalibration C12-Benzene 0.01
Total Aromatics 10.75
